SlowDen › Blog › Embeddability census
We probed 178 developer-submitted browser games for embeddability. 50 refuse. Here is the breakdown by the exact header that refuses, and what it means.
SlowDen lists 178 developer-submitted browser games. We asked a simple question of every one of them: if we put this in an iframe, will the browser allow it?
Not a guess from the page's appearance — a direct read of the response headers, one request per game, run against the live URL each developer gave us.
| Result | Games | Share |
|---|---|---|
| Embeds fine | 128 | 72% |
| Refuses to embed | 50 | 28% |
Better than one in four. If you have ever put a game on a portal and seen a blank rectangle where it should be, this is how common that is.
| Cause | Games |
|---|---|
X-Frame-Options header | 30 |
…of which DENY | 15 |
…of which SAMEORIGIN | 15 |
Content-Security-Policy: frame-ancestors | 13 |
| The URL is simply dead or unreachable | 7 |
Two of those three are deliberate. X-Frame-Options and frame-ancestors
are anti-clickjacking defences, and a lot of hosting platforms set them for you by default —
which is why SAMEORIGIN alone accounts for 15 games. Most of those
developers never chose it.
The third group is different. 7 games point at a URL that no longer works at all:
| Response | Games |
|---|---|
http-403 | 3 |
http-404 | 2 |
http-503 | 1 |
http-436 | 1 |
That is the quiet one. A game submitted months ago, hosted on a free tier, and gone — with nothing on the portal's side to notice, because a dead host is not a loud failure.
A deliberate omission: 4 further games did not respond at all when we probed them, and we do not count those as refusing to embed. One failed request is not evidence — a host can be briefly down. Our checker fails safe and assumes a game is embeddable unless it is actually told otherwise.
A URL can return HTTP 200 and still be dead. One of the games above answers 200, sends no framing headers at all, and then redirects to its host's own "page not found" screen. Every status-code check we had called it healthy. Embedded, a visitor would have seen a 404 page inside the player.
If you run a portal: check the final URL after redirects and the page's title, not the status code. If you submit games: that is also how your listing can look fine to a checker and broken to a player.
Refusing to be framed is a reasonable thing for a developer to do, and we do not ask anyone to turn it off. The portal's job is to notice and respond — so a game that refuses embedding opens in its own tab instead, with the link labelled, rather than showing a blank box and pretending nothing is wrong.
If you want the mechanism rather than the numbers, we wrote that up separately: why your game breaks inside an iframe, and why a browser game loads to a black screen.
Developers can submit a browser game here. Every game is free to play, runs in the browser, and credits the studio that made it.
All 324 free browser games on SlowDen — no download, no sign-up.